Membranes

The Cell Membrane: Structure <div style="display:inline;"><img height="1" width="1" style="border-style:none;" alt="" src="//googleads.g.doubleclick.net/pagead/viewthroughconversion/1001687149/?value=0&label=b1TSCIv8tAUQ7ZDS3QM&guid=ON&script=0"/></div> The Cell Membrane: Structure The fluid Mosaic Model: A phospholipid bi-layer with associated proteins.

Functions: Boundary of Cell Transport of materials in and out of the cell Communication between cell and environment

Membrane Phospholipids: Structure: Lipids with a phosphate attached to glycerol in place of a fatty acid tail. Polar (hydrophilic) phosphate “head”, nonpolar (hydrophobic) fatty acid tails. This type of polar/nonpolar molecule is called “amphipathic”. Spontaneously organizes in the presence of water to form bi-layer Fluid: phospholipids are constantly moving.

Function: Makes a “selectively permeable” membrane. Only small, non-polar molecules can easily move through the phospholipid bi-layer (Why?)

Cholesterol: Structure: Function: steroid lipid Acts as a “temperature buffer” to help maintain membrane fluidity over a range of temperatures. Prevents it from freezing and keeps it from scattering at high temps

Membrane Proteins: Structure: Various, depending on the role they play: Integral proteins: penetrate one or both layers of the bilayer. Peripheral proteins: associated with the membrane, but don’t penetrate the bilayer. The polarity of different regions of a membrane protein vary according to the role of that protein. glycolipid integral peripheral

Results: Membrane proteins are mobile in the cell membrane.

Functions:

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Any Questions?? 2007-2008